1. Field of the Invention
The present invention relates to a synchrotron radiation light-source apparatus and a method of manufacturing the same.
2. Description of the Related Art
One known type of this apparatus is the synchrotron radiation light-source apparatus, shown in FIG. 8, which is described, for example, in the "1-2 GeV Synchrotron Radiation Source, Conceptual Design Report (July 1986)", page 23, published by Lawrence Berkeley Laboratory, University of California, Berkeley. In FIG. 8, reference numeral 1 denotes an orbiting trajectory of an electron beam; reference numeral 2 denotes bending electromagnets disposed at predetermined intervals with respect to the orbiting trajectory 1; reference numeral 3 denotes a focusing quadrapole electromagnet, disposed on the orbiting trajectory 1 before and after the bending electromagnets 2, for converging beams; and reference numeral 4 denotes a defocusing quadrapole electromagnet. FIG. 9 shows a betatron function within the bending electromagnets 2. FIG. 10 shows the coordinate system of the synchrotron radiation light-source apparatus. The horizontal axis S in FIG. 9 indicates the coordinates along the S axis in FIG. 10. Reference letter lB denotes the length of the bending electromagnet.
The operation of the synchrotron radiation light-source apparatus will now be explained. The orbit 1 of an electron beam is bent by the bending electromagnets 2; the electron beam is converged by the focusing quadrapole electromagnet 3 and the defocusing quadrapole electromagnet 4, while emitting synchrotron radiation (referred to as SR), and passes along and encircles a limited area along a closed orbit. The widths along the X and Y axes in the limited area along the closed orbit, i.e., beam sizes, are such that a value called emittance is multiplied by the square root of the betatron function values along the X and Y axes. Since the distribution of the betatron function along the closed orbit is determined by the deflection angle and the magnetic-field gradient of the bending electromagnet 2, by the magnetic-field gradient of the focusing quadrapole electromagnet 3, by the magnetic-field gradient of the defocusing quadrapole electromagnet 4, and by the locations of the electromagnets the value of the betatron function differs depending upon the position on the closed orbit. Also, emittance is determined uniquely for the SR light-source apparatus on the basis of the deflection angle and the magnetic-field gradient of the bending electromagnets 2; by the magnetic-field gradient of the focusing quadrapole electromagnet 3; by the magnetic-field gradient of the defocusing quadrapole electromagnet 4; by the positions at which the electromagnets are positioned; and by the beam energy. Regardless of the position on the closed orbit, the size of the emittance is the same. Emittance is obtained by multiplying a value obtained by integrating a function H(s) (shown in equation (1) below) in the bending electromagnets 2 by a value which is dependent on the beam energy. EQU H (s)=(.eta.(s).sup.2 +(.beta.(s).eta.'(s)-.beta.'(s).eta.(s)/2).sup.2)/2.pi..rho..beta.(s) (1)
where .beta.(s) is the betatron function along the X axis, .rho. is the deflection radius, and .eta. (s), called a dispersion function, is a function whose value, similarly to the betatron function, varies depending upon its position on the closed orbit. Although .eta. (s) does not vary much with respect to changes in the magnetic-field gradients of the bending electromagnets 2, the focusing quadrapole electromagnet 3 and the defocusing quadrapole electromagnet 4, .beta. (s) is a monotonically decreasing function with respect to a negative value of the magnetic-field gradient at position s. Therefore, in the conventional SR light-source apparatus, by making the bending electromagnets 2 have a fixed, negative magnetic-field gradient, the value of .beta. (s) is made small at the bending electromagnets 2 as shown in FIG. 9 so that emittance is made smaller.
However, in the conventional synchrotron radiation tight-source apparatus, since the bending electromagnets 2 are made to have only a fixed magnetic-field gradient, the betatron function has no fixed area along the S axis within bending electromagnets 2. Consequently, the beam size is not fixed. As a result, a problem arises, for example, in that the characteristics of synchrotron radiation generated from the bending electromagnets 2 differ depending upon the position at which they are extracted.